The present invention relates to a press die machine that is used in forming, for example, fuel-cell separators.
There is known a configuration shown in FIG. 10 as a separator used for a fuel cell. The separator is composed of a plate 41 made of a hard material such as titanium, and a plurality of first grooves 411 are formed on a first side face thereof at predetermined intervals. Further, a plurality of second grooves 412 are formed on a second side face on the opposite side of the first side face of the plate 41. Each second groove 412 is arranged between two adjacent first grooves 411. The first and second grooves 411, 412 of the plate 41 constitute respectively gas flow channels of fuel gas (hydrogen) and gas flow channels of oxidation gas (oxygen).
In the case of forming the above-described fuel-cell separator, a press die machine, for example, as shown in FIG. 11, has been conventionally used. The press die machine is provided with a lower die 43, which has an indented die face 431 on an upper face thereof and an upper die 44, which is arranged to move closer to or away from the lower die 43 and has on a lower face thereof an indented die face 441 corresponding to the die face 431 of the lower die 43. In a state in which a plate 41 as a workpiece is placed on the die face 431 of the lower die 43, the upper die 44 moves toward the lower die 43, by which first and second grooves 411, 412 are pressed on the plate 41 between the die faces 431, 441 of the both dies 43, 44.
In the case of manufacturing the lower die 43 and the upper die 44 of the above-described press die machine, a die material is subjected to cutting of the surface to form the indented die faces 431, 441. Where the die material is a super-hard metal material such as high-speed steel in the cutting, a cutting tool easily becomes dull. Therefore, it is difficult to cut indented patterns of the die faces 431, 441 along an extension direction of the indented patterns at one time by using a single cutting tool.
In order to cope with the above-described problem, a press die machine as shown in FIGS. 12 and 13 has been conventionally proposed. In this conventional machine, a lower die 43 is configured to be divided into a plurality of segments 45 formed in a square column shape, etc. These segments 45 are fitted into a frame 47 on a base 46 and arranged to be aligned in a length direction and in a width direction of the frame 47. A space member 48 is placed between each inner side-face of the frame 47 and corresponding segments 45. According to the above-described configuration, each of the segments 45, which are narrow in area, is subjected to cutting of an end face thereof to form an indented face, and the segments 45 are aligned to integrate the indented faces, thus making it possible to form the indented die face 431. Therefore, in this configuration, the die face 431 can be easily cut. As with the lower die 43, the upper die 44 is also formed by aligning the segments 45.
On the other hand, Japanese Laid-Open Patent Publication No. 61-255725 has disclosed a pressing machine in which a pair of upper and lower dies is used to simultaneously form a plurality of elbows flexed in a corrugated shape from a base pipe, with the elbows being adjacent continuously. In this pressing machine, both dies are configured to be divided into a plurality of segments, and each of the segments is provided with a die face having corrugated grooves. The base pipe is placed on a die face of the lower die, and the upper die is moved toward the lower die in a state in which a hydraulic pressure is applied inside the base pipe. Thereby, the elbows are simultaneously formed through pressing between the die faces of the both dies, with the elbows being adjacent continuously.
The above described conventional configurations have the following drawbacks.
In the conventional configuration described in FIGS. 12 and 13, joint portions 451 between two adjacent segments 45 are arranged to face each other between the both dies 43, 44. As shown in FIG. 13, when the plate 41 is pressed between the both dies 43, 44, a middle portion on a side face of each of the segments 45 of both dies 43, 44 is deformed to expand outward by a pressure applied at the time of pressing. The deformation of each segment 45 exerts a force that produces a gap between two adjacent segments 45. On the other hand, gaps on opposite sides of the plate 41, which is located between the both dies 43, 44, are positioned to correspond to each other. Therefore, stress acting on the plate 41 is changed abruptly at each joint portion 451 between two segments 45, thereby developing along the joint portion 451 a step 49 that is not necessary for the plate 41.
Further, the conventional configuration disclosed in the above-described Japanese Laid-Open Patent Publication No. 61-255725 is different from the machine filed in the present application not only in the shape of a workpiece to be pressed but also in the technical field of a product after being pressed, with no relationship found between the functions and use purposes. The machine disclosed in Japanese Laid-Open Patent Publication No. 61-255725 is to form a tubular elbow having an internal space between the upper and lower dies, and the upper die and the lower die face each other by way of a peripheral wall forming the elbow and fluid inside the elbow. Therefore, the conventional configuration disclosed in Japanese Laid-Open Patent Publication No. 61-255725 is free of any problem of the steps 49 developing on one plate as shown in FIGS. 12 and 13.